Headgear for a horse (6)
I believe the answer is:
bridle
'headgear for a horse' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for bridle that I've seen before include "Take offence" , "A curb; show scorn (at)" , "Bristle" , "Headgear used to control a horse" , "Part of horse's harness that goes on its head" .)